issue503: files do not open

When I follow a link that points to a file and then opt for "open" (o), the file will be downloaded to
/tmp but never opened. Instead, a message is displayed that conkeror waits for the website to answer. If
I opt for "save" (s), conkeror's behaviour is normal.
I am using conkeror (version 160130.1.20.g9f2b548-1) on archlinux together with palemoon (version
26.1.1-1). When using xulrunner this problem does not occur.
Any help is greatly appreciated.

Some additional information:
The problem occurs with Palemoon 26.1 only, the previous version 26.0 was OK in this respect.
Furthermore, the problem looks like being related to Issue 114 (see http://bugs.conkeror.org/issue114),
but the solution proposed there does not work.
Finally, I have succeeded in the meantime to make firefox work together with conkeror [the problems
related to firefox will be reported separately], and fortunately this solves the issue. With Firefox 44,
files are downloaded and opened in an external program as expected.